The present invention relates to a nozzle used in a process for applying a coating composition to an elongated, flexible support (web) which is continuously moving. Such a process may be used in the manufacture of a photosensitive material such as photographic film or paper, pre-sensitized plate, a magnetic recording material such as magnetic recording tape, or a recording material such as pressure-sensitive recording paper or heat-sensitive recording paper.
More particularly, the invention relates to a device for treating the lateral edge parts of a coated layer formed on the web.
In a coating process of this type, the coated layer often has a tendency to rise along both lateral edges of the web to form the edge bead portions due to the surface tension of the coating composition In such a case, the coated layer is not uniformly dried in the following drying process. Accordingly, the edge bead portions should be removed before the drying zone.
U.S. Pat. No. 2,899,339 discloses a method for removing the edge bead portions and a device for practicing the method. In accordance with the method, hollow nozzles for sucking up coating compostion are provided along both lateral edges of a web. Each nozzle has an L-shaped pipe structure. A spray or jet stream of diluent or solvent is supplied from the peripheral part of the nozzle, and coating composition together with diluent or solvent is removed into the central part thereof. The present invention is intended to provide an improved suction nozzle for the same process.
The inventors have practiced the coating process disclosed by the aforementioned patent and found that much of the spray of diluent or solvent supplied from the peripheral part of the nozzle is sucked up before reaching the opening of the nozzle, as a result of which the edge bead portions of the coated layer formed along the edges of the web are not sufficiently removed.
Further, Japanese Laid-Open Patent Application No. 73579/1981 has proposed a coating process in which a liquid is jetted from the central part of a suction nozzle having a dual pipe structure for application to the raised parts of a coated layer, and the liquid and the coating composition of the edge bead portions are sucked into the suction nozzle. However, this method also suffers from difficulties in that the liquid jetted from the central part of the nozzle may flow over to the rear side of the web which should not be coated, or it may foul rollers located near the nozzle.
Accordingly, an object of the present invention is to provide a suction nozzle for removing the lateral edge bead portions of a coated layer in which the above-described difficulties accompanying a conventional suction nozzle have been eliminated, and which operates effectively and causes no contamination.